The present invention relates to a photosensitive composition and a pattern formation method using the same.
With recent increase in the scale of integration and the packing density in solid state devices, it is required to form fine patterns at a high efficiency. When an electron beam sensitive composition is used, it is possible to form patterns having a width of, for example, about 1 .mu.m. However, when the electron beam sensitive composition is exposed to electron beams, it is necessary to focus electron beams and apply the focussed electron beams to the surface from one end to the other end in sequence. Accordingly, a long time is required for exposing one workpiece to electron beams. For example, about 20 to about 50 minutes are necessary for exposing one workpiece having a surface area of 10 cm.times.10 cm, though this time varies to some extent depending on the sensitivity of the composition used and the kind of the pattern to be formed. Furthermore, irradiation should be conducted in vacuo and if the time and operation necessary for maintaining workpieces in vacuo are taken into account, exposure to electron beams is not preferred when devices are manufactured in large quantities on an industrial scale.
When a photosensitive composition is used and a workpiece is exposed to light through a mask, a pattern can be formed in a short time. Conventional photosensitive compositions are ordinarily sensitive to rays in the spectral region of 320 to 500 nm. When a workpiece is exposed to light having a wavelength in this region through a mask, because of diffraction and interference effects owing to inherent properties of this light, it is difficult to form a pattern having a width of 1 to 2 .mu.m.
As means for forming such fine patterns, there has been proposed a method using ultraviolet rays of a shorter wavelength (hereinafter referred to as "deep UV light or ray") in the spectral region of 200 to 320 nm, preferably 200 to 300 nm. In this case, the diffraction and interference effects are reduced and finer patterns can be formed. As compounds sensitive to such deep UV light, there are known poly(methyl methacrylate) and poly(methylisopropenyl ketone). However, it has been found that the sensitivity to deep UV light of these compounds is very low and they have no practical utility.